1. Field of the Invention
This invention relates generally to a discrete particle counter and, more particularly, to a seed monitor for counting seeds dispensed by a seed planter through a plurality of seed tubes, where the seed monitor includes an optical sensor attached to each seed tube and one or more electro-optical controllers remotely connected to a group of sensors by optical fibers.
2. Discussion of the Related Art
As is well understood, it is important to monitor the quantity of seeds that are being planted into a planting row, especially in a high capacity agricultural environment such as a farm where the seeds are corn seeds, soy bean seeds and the like. Planting too many seeds causes the resulting plant product to be too closely spaced together to allow for proper plant growth, thus affecting the crop yield. Planting too few seeds reduces the effective use of the planting area. For high output planting, industrial seed planters have been devised to plant a high volume of seeds relatively quickly. To ensure that the proper number of seeds are planted by the seed planters, a seed monitoring system is generally provided that counts the seeds as they are dispensed through seed tubes associated with the planter. A typical seed planter will have many seed tubes for planting a multitude of planting rows simultaneously.
One type of seed monitoring system incorporates optical devices that generate an optical beam directed across the seed tubes, and optical sensors that are sensitive to the loss of light intensity caused by seeds interfering with the optical beam. An electrical counting circuit monitors the occurrences of loss of light intensity to provide a count of the seeds. Various optical seed monitoring systems of this type are disclosed in U.S. Pat. Nos. 3,974,377 issued to Steffen; 4,555,624 issued to Steffen et al.; and 4,163,507 issued to Bell.
These, as well as other, optical seed monitoring systems have been inaccurate for various reasons. One inaccuracy results from the spatial nonuniformity of the optical beam that senses the seeds. Because of spatial nonuniformity, the intensity of optical rays generated by the optical devices vary depending upon the location within the optical beam. Therefore, the ability of the optical sensor to detect the interruption of the optical beam by the seeds varies depending on the location of the seeds within the beam. Consequently, the optical sensor may not adequately detect seeds being dropped through certain locations in the seed chute.
One prior art seed monitoring system has attempted to address spatial nonuniformity of the optical beam of a seed sensor by proposing an optical device that generates a trapezoidal cross-section of an optical beam. However, the trapezoidal cross-section creates an undesirable spatial restriction for groups of seeds as they are dropped through the seed tube. U.S. Pat. No. 4,634,855 issued to Friend et al. also discloses an attempt to create an optical beam of high uniformity. However, this proposed solution is of such complexity that the feasibility for commercial success is limited.
Another drawback of the known optical seed monitoring systems is attributable to the environment in which the optical sensors are operating. Because the seed planters encounter dirt, dust and various chemicals during the planting process that may accumulate in the seed tubes, the sensors may be adversely affected because of contamination of the optical components. This situation is further exasperated in those types of optical sensors in which the optoelectronic components and/or electronic circuits of the sensor are located at or attached to the seed tubes. Other problems arrive by attempting to protect the circuits and associated wire harness connectors from the corrosive effects due to a combination of moisture and the environmental elements.
Another drawback of the known optical seed monitoring systems occurs when the seed sensors are associated with circuitry that counts pulses when the optical beam is interrupted by the seeds. This may result in a count inaccuracy because a plurality of seeds may simultaneously traverse the optical beam and be counted as a single seed. A related problem is that the accuracy of the known optical seed monitoring systems tend to deteriorate with increasing planting speed, with higher seed populations per acre, and with small grains and seeds. These optical systems may be incapable of sufficiently rapid response to reliably count each seed.
What is needed is an optical seed monitoring system that effectively counts each individual seed at a high planting rate, and does not suffer from the drawbacks discussed above. It is therefore an object of the present invention to provide such an optical seed counter.